This is a simple chrome extension that allows you to copy the id of a steam workshop file easily. If you have nothing selected on the workshop page, simply press CTRL + C and it will copy the ID to your clipboard. You can still copy "normally" on workshop pages. For that simply select something on the site.
To install this extension, go to your extension page and enable the developer mode. Then click on "Load unpacked" and select the folder with the extension files.